Light emitting diode device

ABSTRACT

Described are light emitting diode (LED) devices including a combination of electroluminescent quantum wells and photo-luminescent active regions in the same wafer. A first group of QWs with shortest emission wavelength is placed between the p- and n-layers of a p-n junction. Other groups of QWs with longer wavelengths are placed outside the p-n junction in a part of the LED structure where electrical injection of minority carriers does not occur. Electroluminescence emitted by the first group of QWs is absorbed by other group(s) and re-emitted as longer wavelength light. The color of an individual die made on the wafer can be controlled by either etching away unwanted groups of longer-wavelength QWs at the position of that die, or keeping them intact. Wavelength-selective mirrors that increase down conversion efficiency may be selectively applied to die where longer wavelength emission is desired. The use of tunnel junction contacts facilitates integration of wavelength selective mirrors to external surfaces of the die and avoids problems of conductivity type conversion on etched p-GaN layers.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.17/155,499, filed on Jan. 22, 2021, which claims priority to U.S.Provisional Application No. 63/126,038, filed Dec. 16, 2020, the entiredisclosures of which are hereby incorporated by reference herein.

TECHNICAL FIELD

Embodiments of the disclosure generally relate to arrays of lightemitting diode (LED) devices and methods of manufacturing the same. Moreparticularly, embodiments are directed to light emitting diode devicesincluding photoluminescent quantum wells and electroluminescent quantumwells, and a bilayer contact.

BACKGROUND

A light emitting diode (LED) is a semiconductor light source that emitsvisible light when current flows through it. LEDs combine a P-typesemiconductor with an N-type semiconductor. LEDs commonly use aIII-group compound semiconductor. A III-group compound semiconductorprovides stable operation at a higher temperature than devices that useother semiconductors. The III-group compound is typically formed on asubstrate formed of sapphire or silicon carbide (SiC).

Typically, color LED displays are manufactured by picking LEDs fromseparate blue, green and red emitting wafers and then aligning them inalternating close proximity on the display. This method is difficult toapply for high resolution displays which require micron-sized LEDpixels. As the die size decreases to satisfy resolution requirements,larger and larger numbers of die must be transferred at each pick andplace operation to populate a display of given dimensions. ManufacturingLED displays would be greatly simplified if LEDs of the three primarycolors could be fabricated at controlled positions within the samesemiconductor wafer.

Accordingly, there is a need for LED devices where LEDs of differentcolors are in the same wafer.

SUMMARY

Embodiments of the disclosure are directed to LED devices and methodsfor manufacturing LED devices. In one or more embodiments, a lightemitting diode (LED) device comprises: a first sub-pixel comprising afirst anode contact on a first mesa, the first mesa having a first mesatunnel junction on a first mesa electroluminescent quantum well on afirst mesa n-type layer on a substrate; a second sub-pixel comprising asecond anode contact on a second mesa, the second mesa having a secondmesa first photoluminescent quantum well and a second mesa secondphotoluminescent quantum well on a second mesa tunnel junction on asecond mesa electroluminescent quantum well on a second mesa n-typelayer on the substrate; a third sub-pixel comprising a third anodecontact on a third mesa, the third mesa having a third mesaphotoluminescent quantum well on a third mesa tunnel junction on a thirdmesa electroluminescent quantum well on a third mesa n-type layer on thesubstrate; a first trench separating the first sub-pixel and the secondsub-pixel; a second trench separating the second sub-pixel and the thirdsub-pixel; and a dielectric layer formed over at least a portion of thefirst sub-pixel, the second sub-pixel, and the third sub-pixel.

Other embodiments of the disclosure are directed to a light emittingdiode (LED) system comprising: a light emitting diode (LED) arraycomprising a first sub-pixel adjacent to a second sub-pixel, the secondsub-pixel adjacent to a third sub-pixel; the first sub-pixel, secondsub-pixel, and third sub-pixel separated by one or more trenches, adielectric layer formed over at least a portion of the first sub-pixel,the second sub-pixel, and the third sub-pixel; the first sub-pixelcomprising a first mesa having a first mesa tunnel junction on a firstmesa electroluminescent quantum well on a first mesa n-type layer, thesecond sub-pixel comprising a second mesa having a second mesa firstphotoluminescent quantum well and a second mesa second photoluminescentquantum well on a second mesa tunnel junction on a second mesaelectroluminescent quantum well on a second mesa n-type layer, the thirdsub-pixel comprising a third mesa having a third mesa photoluminescentquantum well on a third mesa tunnel junction on a third mesaelectroluminescent quantum well on a third mesa n-type layer; an LEDdevice attach region having a first electrode coupled to a first anodecontact on the first sub-pixel, a second electrode coupled to a secondanode contact on the second sub-pixel, and a third electrode coupled toa third anode contact on the third sub-pixel; and driver circuitryconfigured to provide independent voltages to one or more of the firstelectrode, the second electrode, and the third electrode.

One or more embodiments are directed to a method of manufacturing an LEDdevice. In one or more embodiments, the method comprises: forming anucleation layer on a substrate; forming a defect reduction layer on thenucleation layer; forming an n-type layer on the defect reduction layer;forming at least one electroluminescent quantum well on the n-typelayer; forming a tunnel junction on the at least one electroluminescentquantum well; forming a n-type layer on the tunnel junction; forming atleast one first photoluminescent quantum well on the n-type layer;forming at least one second photoluminescent quantum well on the atleast one first photoluminescent quantum well; forming a first mesa, asecond mesa, and a third mesa, the first mesa and the second mesaseparated by a first trench, the second mesa and the third mesaseparated by a second trench; removing the at least one firstphotoluminescent quantum well and the at least one secondphotoluminescent quantum well from the first mesa; removing the at leastone second photoluminescent quantum well from the third mesa;conformally depositing a dielectric layer on the first mesa, the secondmesa, and the third mesa; forming a contact hole in the first mesa, thesecond mesa, and the third mesa; and forming a first contact on thefirst mesa, a second contact on the second mesa, and a third contact onthe third mesa.

Embodiments of the disclosure are directed to LED devices and methodsfor manufacturing LED devices. In one or more embodiments, a lightemitting diode (LED) device comprises: a first sub-pixel comprising afirst cathode contact on a first mesa, the first mesa having first mesaelectroluminescent quantum well on a first mesa tunnel junction on a ona first mesa n-type layer; a second sub-pixel comprising a secondcathode contact on a second mesa, the second mesa having a second mesafirst photoluminescent quantum well and a second mesa secondphotoluminescent quantum well on a second mesa electroluminescentquantum well on a second mesa tunnel junction on a second mesa n-typelayer; a third sub-pixel comprising a third cathode contact on a thirdmesa, the third mesa having a third mesa photoluminescent quantum wellon a third mesa electroluminescent quantum well on a third mesa tunneljunction on a third mesa n-type layer; a first trench separating thefirst sub-pixel and the second sub-pixel; a second trench separating thesecond sub-pixel and the third sub-pixel; and a dielectric layer formedover at least a portion of the first sub-pixel, the second sub-pixel,and the third sub-pixel.

Other embodiments of the disclosure are directed to a light emittingdiode (LED) system comprising: a light emitting diode (LED) arraycomprising a first sub-pixel adjacent to a second sub-pixel, the secondsub-pixel adjacent to a third sub-pixel; the first sub-pixel, secondsub-pixel, and third sub-pixel separated by one or more trenches, adielectric layer formed over at least a portion of the first sub-pixel,the second sub-pixel, and the third sub-pixel; the first sub-pixelcomprising a first mesa having a first mesa electroluminescent quantumwell on a first mesa tunnel junction on a first mesa n-type layer, thesecond sub-pixel comprising a second mesa having a second mesa firstphotoluminescent quantum well and a second mesa second photoluminescentquantum well on a second mesa electroluminescent quantum well on asecond mesa tunnel junction on a second mesa n-type layer, the thirdsub-pixel comprising a third mesa having a third mesa photoluminescentquantum well on a third mesa electroluminescent quantum well on a thirdmesa tunnel junction on a third mesa n-type layer; an LED device attachregion having a first electrode coupled to a first cathode contact onthe first sub-pixel, a second electrode coupled to a second cathodecontact on the second sub-pixel, and a third electrode coupled to athird cathode contact on the third sub-pixel; and driver circuitryconfigured to provide independent voltages to one or more of the firstelectrode, the second electrode, and the third electrode.

One or more embodiments are directed to a method of manufacturing an LEDdevice. In one or more embodiments, the method comprises ofmanufacturing an LED device comprises: forming a nucleation layer on asubstrate; forming a defect reduction layer on the nucleation layer;forming an n-type layer on the defect reduction layer; forming at leastone first photoluminescent quantum well on the n-type layer; forming atleast one second photoluminescent quantum well on the at least one firstphotoluminescent quantum well; forming at least one electroluminescentquantum well on the second photoluminescent quantum well; forming atunnel junction on the at least one electroluminescent quantum well;forming an n-type layer on the tunnel junction; forming a first mesa, asecond mesa, and a third mesa, the first mesa and the second mesaseparated by a first trench, the second mesa and the third mesaseparated by a second trench; removing the at least one firstphotoluminescent quantum well and the at least one secondphotoluminescent quantum well from the first mesa; removing the at leastone second photoluminescent quantum well from the third mesa;conformally depositing a dielectric layer on the first mesa, the secondmesa, and the third mesa; forming a contact hole in the first mesa, thesecond mesa, and the third mesa; forming a first contact on the firstmesa, a second contact on the second mesa and a third contact on thethird mesa; and removing the substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentdisclosure can be understood in detail, a more particular description ofthe disclosure, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this disclosure and are therefore not to beconsidered limiting of its scope, for the disclosure may admit to otherequally effective embodiments. The embodiments as described herein areillustrated by way of example and not limitation in the figures of theaccompanying drawings in which like references indicate similarelements.

FIG. 1 illustrates a cross-sectional view of an LED device includingmultiple quantum wells according to one or more embodiments;

FIG. 2 illustrates a cross-sectional view of an LED device includingmultiple quantum wells according to one or more embodiments;

FIG. 3 illustrates a cross-sectional view of an LED device includingmultiple quantum wells according to one or more embodiments;

FIG. 4 illustrates a cross-sectional view of an LED device includingmultiple quantum wells according to one or more embodiments;

FIG. 5 illustrates a cross-sectional view of an LED device includingmultiple quantum wells according to one or more embodiments;

FIG. 6 illustrates a cross-sectional view of an LED device includingmultiple quantum wells according to one or more embodiments;

FIG. 7 illustrates a cross-sectional view of an LED device includingmultiple quantum wells according to one or more embodiments;

FIG. 8 illustrates a cross-sectional view of system according to one ormore embodiments;

FIG. 9 illustrates a cross-sectional view of an LED device includingmultiple quantum wells according to one or more embodiments; and

FIG. 10 illustrates a cross-sectional view of system according to one ormore embodiments;

FIG. 11 illustrates a cross-sectional view of system according to one ormore embodiments;

FIG. 12 illustrates a cross-sectional view of system according to one ormore embodiments;

FIG. 13 illustrates a process flow diagram of a method according to oneor more embodiments;

FIG. 14 illustrates a cross-sectional view of an LED device includingmultiple quantum wells according to one or more embodiments;

FIG. 15A illustrates a cross-sectional view of an LED device includingmultiple quantum wells according to one or more embodiments;

FIG. 15B illustrates a cross-sectional view of an LED device includingmultiple quantum wells according to one or more embodiments;

FIG. 16 illustrates a cross-sectional view of an LED device includingmultiple quantum wells according to one or more embodiments;

FIG. 17 illustrates a cross-sectional view of an LED device includingmultiple quantum wells according to one or more embodiments;

FIG. 18 illustrates a cross-sectional view of an LED device includingmultiple quantum wells according to one or more embodiments;

FIG. 19 illustrates a cross-sectional view of an LED device includingmultiple quantum wells according to one or more embodiments;

FIG. 20 illustrates a cross-sectional view of an LED device includingmultiple quantum wells according to one or more embodiments;

FIG. 21 illustrates a cross-sectional view of an LED device includingmultiple quantum wells according to one or more embodiments;

FIG. 22 illustrates a cross-sectional view of an LED device includingmultiple quantum wells according to one or more embodiments;

FIG. 23 illustrates a cross-sectional view of an LED device includingmultiple quantum wells according to one or more embodiments;

FIG. 24 illustrates a cross-sectional view of an LED device includingmultiple quantum wells according to one or more embodiments;

FIG. 25 illustrates a cross-sectional view of an LED device includingmultiple quantum wells according to one or more embodiments;

FIG. 26 illustrates a cross-sectional view of an LED device includingmultiple quantum wells according to one or more embodiments; and

FIG. 27 illustrates a process flow diagram of a method according to oneor more embodiments.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. The figures are not drawn to scale. For example, theheights and widths of the mesas are not drawn to scale.

DETAILED DESCRIPTION

Before describing several exemplary embodiments of the disclosure, it isto be understood that the disclosure is not limited to the details ofconstruction or process steps set forth in the following description.The disclosure is capable of other embodiments and of being practiced orbeing carried out in various ways.

The term “substrate” as used herein according to one or more embodimentsrefers to a structure, intermediate or final, having a surface, orportion of a surface, upon which a process acts. In addition, referenceto a substrate in some embodiments also refers to only a portion of thesubstrate, unless the context clearly indicates otherwise. Further,reference to depositing on a substrate according to some embodimentsincludes depositing on a bare substrate or on a substrate with one ormore layers, films, features or materials deposited or formed thereon.

In one or more embodiments, the “substrate” means any substrate ormaterial surface formed on a substrate upon which film processing isperformed during a fabrication process. In exemplary embodiments, asubstrate surface on which processing is performed includes materialssuch as silicon, silicon oxide, silicon on insulator (SOI), strainedsilicon, amorphous silicon, doped silicon, carbon doped silicon oxides,germanium, gallium arsenide, glass, sapphire, and any other suitablematerials such as metals, metal nitrides, III-nitrides (e.g., GaN, AN,InN and other alloys), metal alloys, and other conductive materials,depending on the application. Substrates include, without limitation,light emitting diode (LED) devices. Substrates in some embodiments areexposed to a pretreatment process to polish, etch, reduce, oxidize,hydroxylate, anneal, UV cure, e-beam cure and/or bake the substratesurface. In addition to film processing directly on the surface of thesubstrate itself, in some embodiments, any of the film processing stepsdisclosed is also performed on an underlayer formed on the substrate,and the term “substrate surface” is intended to include such underlayeras the context indicates. Thus for example, where a film/layer orpartial film/layer has been deposited onto a substrate surface, theexposed surface of the newly deposited film/layer becomes the substratesurface.

The term “wafer” and “substrate” will be used interchangeably in theinstant disclosure. Thus, as used herein, a wafer serves as thesubstrate for the formation of the LED devices described herein.

Embodiments described herein describe LED devices and methods forforming LED devices. In particular, the present disclosure describes LEDdevices and methods to produce LED devices which advantageously have twoor more groups of quantum wells (QWs) grown in the same epitaxial wafer.In one or more embodiments, only a first group of QWs with shortestemission wavelength is placed between the p- and n-layers of a p-njunction. Other groups of QWs with longer wavelengths are placed outsidethe p-n junction in a part of the LED structure where electricalinjection of minority carriers does not occur. Electroluminescenceemitted by the first group of QWs is absorbed by other group(s) andre-emitted as longer wavelength light. The color of an individual diemade on the wafer can be controlled by either etching away unwantedgroups of longer-wavelength QWs at the position of that die, or keepingthem intact as will be discussed below. In one or more embodiments,wavelength-selective mirrors that increase down conversion efficiencymay be selectively applied to the die where longer wavelength emissionis desired. In one or more embodiments, the use of tunnel junctioncontacts facilitates integration of wavelength selective mirrors toexternal surfaces of the die and avoids problems of conductivity typeconversion on etched p-GaN layers. The use of tunnel junction contactsfurther relaxes requirements on the conductivity type of the PL-emittingQW group(s) and allows them to be grown at the end of the epitaxy runminimizing the thermal load placed on said QWs by growing other layersof the LED structure.

In one or more embodiments, monolithically integrating LEDs of differentcolors in the same wafer provides advantages compared to a makingdisplays in the conventional method using three wafers of differentcolors. In one or more embodiments, the number of separate epitaxyrecipes which must be manufactured to produce source die for uLEDdisplays is advantageously reduced compared to existing methods,reducing cost and complexity in the epi manufacturing stage. Existingmethods require production of separate blue, green, and red recipes.

In one or more embodiments, the number of pick and place operationsrequired to populate a display is reduced, since arrays of pixels can betransferred together, instead of only one color type pixel at a time.Fewer pick and place operations will advantageously lead to cost andthroughput improvements at the display assembly stage.

Some embodiments eliminate entirely the need for pick and place andinstead allow whole wafer-level transfer of pixels onto a display sinceone wafer can contain all 3 required colors. The entire processed waferor a large piece of it could be incorporated directly into the display.

In one or more embodiments, because the color conversion layers arealready built-in to the wafer during epitaxial growth, separatepost-epitaxy processing steps to add color conversion materials are notrequired. Fundamental technical difficulties associated with (forexample) accurately coating color-converting quantum dots intomicron-sized spaces are, thus, avoided. Additionally, in one or moreembodiments, the efficiency of green or red-emitting LEDs canpotentially be higher than that of conventional LEDs of the same color,particularly for high drive current densities.

In one or more embodiments, the growth of only one tunnel junction andone p-GaN layer to produce three colors is required. Accordingly, theepitaxial growth is less complex versus other epitaxial growth methodsutilizing tunnel junctions to produce LEDs of different colors on thesame wafer.

The embodiments of the disclosure are described by way of the Figures,which illustrate devices (e.g. transistors) and processes for formingdevices in accordance with one or more embodiments of the disclosure.The processes shown are merely illustrative possible uses for thedisclosed processes, and the skilled artisan will recognize that thedisclosed processes are not limited to the illustrated applications.

One or more embodiments of the disclosure are described with referenceto the Figures. FIGS. 1 through 8 illustrate cross-sectional views of adevice 100 according to one or more embodiments. An aspect of thedisclosure pertains to a method of manufacturing a LED array. Referringto FIG. 1 , a LED device 100 is manufactured containing two or moregroups of quantum wells of different emission wavelengths in the samewafer. In one or more embodiments, a first group of quantum wells (withshortest emission wavelength) is located between a p-type layer and afirst n-type layer which forms a p-n junction with the p-type layer. Inone or more embodiments, a tunnel junction connects the p-layer of thep-n junction with a second n-type layer at a different position in theepitaxy stack versus the first n-type layer. In one or more embodiments,second and third groups of quantum wells with longer emissionwavelengths are located within the second n-type layer placed betweenthem and the p-n junction. In one or more embodiments, a tunnel junctionconnects the p-layer of the p-n junction with the second n-type layer.

In one or more embodiments, the first part of the epitaxy involves thegrowth of a nucleation layer 122, a defect reduction layer 120, and ann-type layer 118 and may be the same as in a conventional LED growth runusing a sapphire or other applicable growth substrate 102. In one ormore embodiments, the n-type layer 118 may comprise an n-type currentspreading layer.

The substrate 102 may be any substrate known to one of skill in the artwhich is configured for use in the formation of LED devices. In one ormore embodiments, the substrate 102 comprises one or more of sapphire,silicon carbide, silica (Si), quartz, magnesium oxide (MgO), zinc oxide(ZnO), spinel, and the like. In one or more embodiments, the substrate102 is a transparent substrate. In specific embodiments, the substrate102 comprises sapphire. In one or more embodiments, the substrate 102 isnot patterned prior to formation of the LEDs. Thus, in some embodiments,the substrate is 102 not patterned and can be considered to be flat orsubstantially flat. In other embodiments, the substrate 102 is apatterned substrate.

In one or more embodiments, the n-type layer 118 may comprise any GroupIII-V semiconductors, including binary, ternary, and quaternary alloysof gallium (Ga), aluminum (Al), indium (In), and nitrogen (N), alsoreferred to as III-nitride materials. Thus, in some embodiments, then-type layer 118 comprises one or more of gallium nitride (GaN),aluminum nitride (AlN), indium nitride (InN), gallium aluminum nitride(GaAlN), gallium indium nitride (GaInN), aluminum gallium nitride(AlGaN), aluminum indium nitride (AlInN), indium gallium nitride(InGaN), indium aluminum nitride (InAlN), and the like. In a specificembodiment, the n-type layer 118 comprises gallium nitride (GaN). In oneor more embodiments, the n-type layer 118 is doped with n-type dopants,such as silicon (Si) or germanium (Ge). The n-type layer 118 may have adopant concentration significant enough to carry an electric currentlaterally through the layer.

In one or more embodiments, the layers of III-nitride material whichform the first LED, the second LED and the third LED are deposited byone or more of sputter deposition, atomic layer deposition (ALD),metalorganic chemical vapor deposition (MOCVD), physical vapordeposition (PVD), plasma enhanced atomic layer deposition (PEALD), andplasma enhanced chemical vapor deposition (PECVD).

“Sputter deposition” as used herein refers to a physical vapordeposition (PVD) method of thin film deposition by sputtering. Insputter deposition, a material, e.g. a III-nitride, is ejected from atarget that is a source onto a substrate. The technique is based on ionbombardment of a source material, the target. Ion bombardment results ina vapor due to a purely physical process, i.e., the sputtering of thetarget material.

As used according to some embodiments herein, “atomic layer deposition”(ALD) or “cyclical deposition” refers to a vapor phase technique used todeposit thin films on a substrate surface. The process of ALD involvesthe surface of a substrate, or a portion of substrate, being exposed toalternating precursors, i.e. two or more reactive compounds, to deposita layer of material on the substrate surface. When the substrate isexposed to the alternating precursors, the precursors are introducedsequentially or simultaneously. The precursors are introduced into areaction zone of a processing chamber, and the substrate, or portion ofthe substrate, is exposed separately to the precursors.

As used herein according to some embodiments, “chemical vapordeposition” refers to a process in which films of materials aredeposited from the vapor phase by decomposition of chemicals on asubstrate surface. In CVD, a substrate surface is exposed to precursorsand/or co-reagents simultaneous or substantially simultaneously. Aparticular subset of CVD processes commonly used in LED manufacturinguse metalorganic precursor chemical and are referred to as MOCVD ormetalorganic vapor phase epitaxy (MOVPE). As used herein, “substantiallysimultaneously” refers to either co-flow or where there is overlap for amajority of exposures of the precursors.

As used herein according to some embodiments, “plasma enhanced atomiclayer deposition (PEALD)” refers to a technique for depositing thinfilms on a substrate. In some examples of PEALD processes relative tothermal ALD processes, a material may be formed from the same chemicalprecursors, but at a higher deposition rate and a lower temperature. Ina PEALD process, in general, a reactant gas and a reactant plasma aresequentially introduced into a process chamber having a substrate in thechamber. The first reactant gas is pulsed in the process chamber and isadsorbed onto the substrate surface. Thereafter, the reactant plasma ispulsed into the process chamber and reacts with the first reactant gasto form a deposition material, e.g. a thin film on a substrate.Similarly to a thermal ALD process, a purge step may be conductedbetween the deliveries of each of the reactants.

As used herein according to one or more embodiments, “plasma enhancedchemical vapor deposition (PECVD)” refers to a technique for depositingthin films on a substrate. In a PECVD process, a source material, whichis in gas or liquid phase, such as a gas-phase III-nitride material or avapor of a liquid-phase III-nitride material that have been entrained ina carrier gas, is introduced into a PECVD chamber. A plasma-initiatedgas is also introduced into the chamber. The creation of plasma in thechamber creates excited radicals. The excited radicals are chemicallybound to the surface of a substrate positioned in the chamber, formingthe desired film thereon.

In one or more embodiments, a LED device 100 is manufactured by placingthe substrate 102 in a metalorganic vapor-phase epitaxy (MOVPE) reactorso that the LED device layers are grown epitaxially.

In one or more embodiments, a nucleation layer 122 is formed on thesubstrate 102 prior to the defect reduction layer 120. In one or moreembodiments, the nucleation layer comprises a III-nitride material. Inspecific embodiments, the nucleation layer 122 comprises gallium nitride(GaN) or aluminum nitride (AlN).

In one or more embodiments, a plurality of electroluminescence emittingquantum wells 114 is grown on the current spreading layer 108, with adilute indium concentration layer(s) 116 optionally grown before theelectroluminescence emitting quantum wells 114. In one or moreembodiments, the electroluminescence emitting quantum wells 114 may bedoped with n-type doping.

The electroluminescence emitting quantum wells 114 may be formed usingany deposition technique known to one of skill in the art. Theelectroluminescence emitting quantum wells 114 may comprise a sequenceof multiple quantum wells emitting the same wavelength of light. In oneor more embodiments, the electroluminescence emitting quantum wells 114emit light having a wavelength in a range of from about 410 nm to about495 nm. The electroluminescence emitting quantum wells 114 may comprisedifferent layers of indium gallium nitride (InGaN) and gallium nitride(GaN). The emission color may be controlled by the relative molefractions of indium (In) and gallium (Ga) in the InGaN layer and/or bythe thicknesses of the multiple quantum wells.

In one or more embodiments, an individual quantum well within theelectroluminescence emitting quantum wells 114 may have an InGaNthickness in a range of from about 0.5 nm to about 10 nm and a GaNbarrier thickness in a range of from about 2 nm to about 100 nm. Thetotal number of quantum wells in the electroluminescence emittingquantum wells 114 may be in a range of from 1 to 50.

In one or more embodiments, after the growth of the electroluminescenceemitting quantum wells 114, electron blocking layers and p-type layers112 are grown using deposition techniques known to one of skill in theart. In one or more embodiments, the p-type layers 112 comprise galliumnitride (GaN).

After completing the p-type layer 112 of the LED, the growth conditionsare then changed to grow a tunnel junction 110. In one or moreembodiments, the tunnel junction 110 may be similar to, but is notlimited to, tunnel junctions known to one of skill in the art. After thegrowth of the tunnel junction 110, an n-type layer 104 is grown on thetunnel junction 110. The n-type layer 104 may be thin, or it could bemuch thicker with thickness in the tens or hundreds of nanometers.

In one or more embodiments, the doping concentration of the n-type layer104 may be high enough to facilitate formation of ohmic contacts withcommon metals such as Al, but the doping concentration of the n-typelayer 104 need not be as high as that of the tunnel junction 110. In oneor more embodiments, the n-type layer 104 could have a graded dopingconcentration or it could be divided into several sections withdifferent doping concentrations.

After formation of the n-type layer 104, a group of photoluminescencequantum wells 108 is grown. In one or more embodiments, thephotoluminescence quantum wells 108 emit light having a wavelength in arange of from about 460 nm to about 570 nm. In one or more embodiments,the design of the photoluminescence quantum wells 108 may differ fromthe active region of a conventional green LED in that the n-type dopingconcentration and the number of wells may be different, among otherpossible differences. In one or more embodiments, the dopingconcentration in the photoluminescence quantum wells 108 is set highenough to avoid a significant voltage drop when this layer is part ofthe LED circuit. Subsequently, a second n-type layer 104 is grown on thephotoluminescence quantum wells 108. The second n-type layer 104 b hasthe same doping requirements as first n-type layer 104 a, but the firstn-type layer 104 a and the second n-type layer 104 b may have differentthicknesses.

In one or more embodiments, a second group of photoluminescence quantumwells 106 is grown on a top surface of the second n-type layer 104 b. Inone or more embodiments, the photoluminescence quantum wells 106 emitlight having a wavelength in a range of from about 600 nm to about 750nm. In one or more embodiments, the design of the photoluminescencequantum wells 106 may differ from the active region of a conventional(red) LED in that the n-type doping concentration and the number ofwells may be different, among other possible differences. Finally, athird n-type layer 104 c may be grown over the photoluminescence quantumwells 106. The third n-type layer 104 c has the same doping requirementsas first n-type layer 104 a and the second n-type layer 104 b, but thefirst n-type layer 104 a, the second n-type layer 104 b, and the thirdn-type layer 104 c may have different thicknesses.

It should be noted that the positions of photoluminescence quantum wells108 and the photoluminescence quantum wells 106 within the epitaxy stack101 could be interchanged in one or more embodiments. In one or moreembodiments, locating the photoluminescence quantum wells 108 closer tothe p-n junction (the arrangement illustrated in FIG. 1 ) has theadvantage that light emitted by photoluminescence quantum wells 108 inthe direction of the substrate cannot be absorbed by thephotoluminescence quantum wells 106, thus increasing the green LEDefficiency. It has the disadvantage, however, that blueelectroluminescence is absorbed in the photoluminescence quantum wells108 before it reaches the photoluminescence quantum wells 106, which mayreduce the red LED efficiency. The absorption coefficient of green lightin the photoluminescence quantum wells 106 is not necessarily high.Depending on the internal quantum efficiency (IQE) values and absorptioncoefficients of the photoluminescence quantum wells 106 andphotoluminescence quantum wells 108, an arrangement with the positionsof QWs interchanged versus that depicted in FIG. 1 may be favorable forsome applications.

Referring to FIG. 2 , a plurality of subpixels is formed by etching afirst subpixel 105 a, a second subpixel 105 b, and a third subpixel 105c into the wafer 101. In one or more embodiments, the first subpixel 105a and the second subpixel 105 b are separated by a trench 107 a. In someembodiments, the trench 107 a may be formed using a conventionaldirectional etching process, such as dry etching. The trench 107 a maybe any suitable depth and may extend from the top surface of the thirdn-type layer 104 c through the nucleation layer 122 to the substrate102. The trench 107 a may comprise at least one sidewall 109 a and abottom surface 111 a. In one or more embodiments, the second subpixel105 b and the third subpixel 105 c are separated by a trench 107 b. Insome embodiments, the trench 107 b may be formed using a conventionaldirectional etching process, such as dry etching. The trench 107 b maybe any suitable depth and may extend from the top surface of the thirdn-type layer 104 c through the nucleation layer 122 to the substrate102. The trench 107 b may comprise at least one sidewall 109 b and abottom surface 111 b.

In one or more embodiments, the first subpixel 105 a may have a height(thickness) that is less than the height (thickness) of the secondsubpixel 105 b and less than the height (thickness) of the thirdsubpixel 105 c. In one or more embodiments, the third subpixel 105 c mayhave a height (thickness) that is less than the height (thickness) ofthe second subpixel 105 b.

In one or more embodiments, the etched surface (trench 107 a, 107 b) mayhave an angle of inclination up to 45 degrees. In some embodiments, theetched surface (trench 107 a, 107 b) may be completely vertical.

In one or more embodiments, the formation of the plurality of subpixels105 a, 105 b, 105 c involves an additional etching step compared toconventional LED manufacturing methods. In one or more embodiments, theadditional etching step removes the first group of photoluminescentquantum wells 108 and the second group of photoluminescent quantum wells106 at a first set of positions 105 a on the substrate 102, removes thesecond group of photoluminescent quantum wells 106 at a second set ofpositions 105 c on the substrate 102, and leaves unetched a third set ofpositions 105 b on the substrate 102. The thickness of material thatneeds to be etched from the first set of positions 105 a is thicker thanthat to be removed from the second set of positions 105 c. The thicknessdifference may be accommodated either by separating the additional etchprocess into two separate etch steps, or by coating a sacrificial layeronto the second set of positions 105 c to reduce the depth of materialetched at those positions in a single etch step. Dry etching usingprocess conditions which favor a high vertical/lateral etch rate may beused for the additional etching step. This additional etching step maybe one of the first steps in the process, or it may come later in theprocess (for example, after the mesa etch to expose the n-layer underthe p-n junction).

In one or more embodiments, the first subpixel 105 a is a mesacomprising electroluminescence emitting quantum wells 114. Morespecifically, the first subpixel 105 a comprises a first mesa includinga first n-type layer 104 a on a tunnel junction 110 on electron blockinglayers and p-type layers 112. The p-type layers 112 are onelectroluminescence emitting quantum wells 114. The electroluminescenceemitting quantum wells may be on an optional dilute indium concentrationlayer 116 on an n-type layer 118, on a defect reduction layer 120, on anucleation layer 122, on the substrate 102.

In one or more embodiments, the second subpixel 105 b is a mesacomprising a first group of photoluminescent quantum wells 108 and asecond group of photoluminescent quantum wells 106 on anelectroluminescent quantum well 114. More specifically, the secondsubpixel 105 b comprises a second mesa including a third n-type layer104 c on the second group of photoluminescent quantum wells 106, asecond n-type layer 104 b on the first group of photoluminescent quantumwells 108, a first n-type layer 104 a on a tunnel junction 110 onelectron blocking layers and p-type layers 112. The p-type layers 112are on electroluminescence emitting quantum wells 114. Theelectroluminescence emitting quantum wells 114 may be on an optionaldilute indium concentration layer 116 on an n-type layer 118, on adefect reduction layer 120, on a nucleation layer 122, on the substrate102.

In one or more embodiments, the third subpixel 105 c is a mesacomprising a first group of photoluminescent quantum wells 108 on anelectroluminescent quantum well 114. More specifically, the thirdsubpixel 105 c comprises a third mesa including a second n-type layer104 b on the first group of photoluminescent quantum wells 108, a firstn-type layer 104 a on a tunnel junction 110 on electron blocking layersand p-type layers 112. The p-type layers 112 are on electroluminescenceemitting quantum wells 114. The electroluminescence emitting quantumwells 114 may be on an optional dilute indium concentration layer 116 onan n-type layer 118, on a defect reduction layer 120, on a nucleationlayer 122, on the substrate 102.

In one or more embodiments, a p-type layer activation annealing step maybe performed after the plurality of subpixels are etched because it isdifficult for hydrogen to pass through n-type layers 104 a, 104 b, 105 cand annealing after the mesa etch allows hydrogen to escape laterallyfrom the etched sidewalls.

FIG. 3 shows formation of a dielectric layer 124 on the pluralities ofsubpixels 105 a, 105 b, 105 c and in the trench 107 a, 107 b. Thedielectric layer 124 may be formed using a conventional depositiontechnique, such as, for example, CVD, PECVD, ALD, evaporation,sputtering, chemical solution deposition, spin-on deposition, or otherlike processes.

As used herein, the term “dielectric” refers to an electrical insulatormaterial that can be polarized by an applied electric field. In one ormore embodiments, the dielectric layer 124 may comprise any suitabledielectric material known to the skilled artisan. In some embodiments,the dielectric material comprises one of more of silicon nitride (SiN),titanium oxide (TiO_(x)), niobium oxide (NbO_(x)), aluminum oxide(AlO_(x)), hafnium oxide (HfO_(x)), tantalum oxide (TaO_(x)), aluminumnitride (AlN), silicon oxide (SiO_(x)), and hafnium-doped silicondioxide (HfSiO_(x)). While the term “silicon oxide” may be used todescribe the dielectric layer 124, the skilled artisan will recognizethat the disclosure is not restricted to a particular stoichiometry. Forexample, the terms “silicon oxide” and “silicon dioxide” may both beused to describe a material having silicon and oxygen atoms in anysuitable stoichiometric ratio. In one or more embodiments, thedielectric layer 124 has a thickness greater than about 300 nm, orgreater than about 500 nm, or greater than about 1000 nm.

In one or more embodiments, the dielectric layer 124 is substantiallyconformal. As used herein, a layer which is “substantially conformal”refers to a layer where the thickness is about the same throughout(e.g., on the top surface of each subpixel, on the at least one sidewall109 a, 109 b, and on the bottom surface 111 a, 111 b of the trench 107a, 107 b). A layer which is substantially conformal varies in thicknessby less than or equal to about 5%, 2%, 1% or 0.5%.

In some embodiments, the dielectric layer 124 forms on the bottomsurface 111 a, 111 b of the trench 107. In other embodiments, thedielectric layer 124 is not on the bottom surface 111 a, 111 b of thetrench 107 a, 107 b and the substrate 102 is exposed on the bottomsurface of the trench 107 a, 107 b. Referring to FIG. 4 , portions ofthe dielectric layer 124 may be removed from the bottom surface 111 a,111 b and at least one sidewall 109 a, 109 b of the trench 107 a, 107 b.The portions of the dielectric layer 124 may be removed using aconventional directional etching process, such as dry etching. In one ormore embodiments, when portions of the dielectric layer 124 are removedfrom the bottom surface 111 a, 111 b and at least one sidewall 109 a,109 b of the trench 107 a, 107 b, an exposed portion 125 a, 125 b isformed. The exposed portion 125 a, 125 b may include portions of then-type layer 118, the defect reduction layer 120, the nucleation layer122, and the substrate 102 may be exposed in the trench 107 a, 107 b.

Referring to FIG. 5 , in one or more embodiments, a cathode contactmetal 126, or an n-type contact, is deposited on the exposed portion 125in the trench 107 a, 107 b. The LEDs in the array may, thus, share acommon n-contact electrode as depicted in FIG. 6A. In one or moreembodiments, the cathode contact metal 126 may comprise any suitablematerial known to the skilled artisan. In one or more embodiments, thecathode contact metal 126 comprises an n-contact material selected fromone or more of aluminum (Al), titanium (Ti), and chromium (Cr).

FIG. 6 shows formation of a contact hole 128 in the dielectric layer124, exposing a top surface of the n-type layer 104 In some embodimentsa first contact hole 128 a is formed in the dielectric layer 124 of thefirst subpixel 105 a, exposing a top surface of the first n-type layer104 a. A second contact hole 128 b may be formed in the dielectric layer124 of the second subpixel 105 b, exposing a top surface of the thirdn-type layer 104 c. A third contact hole 128 c may be formed in thedielectric layer 124 of the third subpixel 105 c, exposing a top surfaceof the second n-type layer 104 b. The contact hole 128 a, 128 b, 128 cmay be formed using a conventional directional etching process, such asdry etching.

Referring to FIG. 7 , an anode contact metal 130 is deposited in thecontact hole 128. In one or more embodiments, the anode contact metal130 may comprise any suitable material known to the skilled artisan. Inone or more embodiments, the anode contact metal 130 comprises ap-contact material selected from one or more of aluminum (Al), silver(Ag), gold (Au), platinum (Pt), and palladium (Pd). In specificembodiments, the anode contact metal 130 comprises silver (Ag). In someembodiments, additional metals may be added in small quantities to theanode contact metal as adhesion promoters. Such adhesion promoters,include, but are not limited to, one or more of nickel (Ni), titanium(Ti), and chromium (Cr).

In one or more embodiments, the anode contact 130 and the cathodecontact 126 may be made with the same metal in the same deposition andlift-off steps.

The dielectric passivation layer 124 is shown as a single layer in theFigures, but it could alternatively be implemented as a multilayercoating of high and low refractive index materials with thicknessesoptimized for maximum reflectivity in blue wavelengths. If implementedas a single layer, the optical thickness of the dielectric passivationlayer 124 may be co-optimized with the cathode metal 126 to maximizereflectivity at blue wavelengths. The cathode contact 126 may be made tothe n-type layer on the sides of the mesas 105 a, 105 b, 105 c, makingpossible the use of a single mesa etch step to isolate the LEDs fromeach other and expose the cathode contact for metallization.

In later stages of processing, the spaces between the mesas 105 a, 105b, 105 c are filled with an electrically conductive material 146, whichcould be, for example, electroplated copper (Cu). The entire wafer 100or a piece of the wafer 100, which could be as small as an individualpixel containing three microLED sub-pixels, are bonded to a systemsubstrate 140 such as a display backplane to form a system 200. An arrayof landing pads 142, 144 is arranged on the system substrate 140 withdimensions aligned to those of the bonding pads on the LED wafer 100.The landing pads 142, 144 may be connecting to display driver circuitryin the system substrate 140. The landing pads 142, 144 may includesub-pixels of different heights to accommodate the differences inheights of the LEDs on the wafer, as shown in FIG. 8 . Alternatively,the landing pads 142, 144 may be made from a material that is softenough to accommodate the height differences by mechanical deformationin the bonding process. In one or more embodiments, the bondingmechanism may be based on application of pressure, localized heating, ora combination of the two.

Referring to FIG. 8 , n one or more embodiments, after bonding, thegrowth substrate 102 is removed using a process such as laser lift-offif the substrate is a UV-transparent material such as sapphire. Othertypes of growth substrate may be removed by selective chemical etching.In one or more embodiments, wavelength selective reflector coatings 132,134 are applied to the exposed surfaces of the sub-pixels 105 b, 105 cto prevent color contamination of those pixels with shorter wavelengthlight that is not completely absorbed in the QWs of longer wavelength.In some embodiments, the wavelength selective reflector coatings 132,134 may comprise dichroic mirrors.

In one or more specific embodiments, the wavelength selective reflectorcoating 132 for the third sub-pixel 105 c may be a distributed Braggreflector (DBR) consisting of a repeated stack of dielectric materialswith high and low refractive indices and thicknesses optimized tomaximize reflectivity at the blue electroluminescence peak wavelength.In one or more embodiments, the second sub-pixel 105 b may use twoconnected distributed Bragg reflectors (DBR) optimized for highreflectivity at blue and green wavelengths, respectively, as wavelengthselective reflector coatings 132, 134. In one or more embodiments, thewavelength selective reflector coatings 132, 134 may be patterned bylithographic methods, or using shadow masks if the sub-pixel dimensionsare large enough.

In one or more embodiments, the growth substrate 102 comprises anoptically transparent material such as, but not limited to, sapphire,magnesium oxide (MgO), quartz, and the like. A much shallower mesa etchmay be used, not extending all the way to the substrate, and therequirement for a filler material 146, such as electrodeposited Cu, toplanarize the surface after mesa etching can be avoided. In one or moreembodiments, these differences may simplify the requirements for landingpads 142, 144 on the receiver substrate, though some small heightdifferences may still need to be accommodated. In one or moreembodiments, the substrate 102 may be thinned and optically polishedbefore bonding, but is not removed after bonding. In one or moreembodiments, after deposition and patterning of the wavelength-selectivecoatings 132, 134, an opaque grid may be coated over the substrate toprevent optical cross talk between sub-pixels.

FIG. 9 illustrates an alternative embodiment. The epitaxial growthillustrated in FIG. 9 differs slightly from that of FIGS. 1 through 8 .Referring to FIG. 9 , in one or more embodiments, two epitaxialreflectors 136, 138 are grown before the n-type layer 118 that is underthe p-n junction. The epitaxial reflectors 136, 138 may be dichroicmirrors in some embodiments. In specific embodiments, the epitaxialreflectors 136, 138 may be distributed Bragg reflectors (DBR) comprisedof a sequence of alternating layers III-nitride materials with differentrefractive indices, such as, but not limited to, gallium nitride (GaN)and aluminum gallium nitride (AlGaN) or aluminum indium nitride (AlInN),or mixtures thereof. In one or more embodiments, implementations inwhich post-growth processing to oxidize or introduce porosity into oneof the materials of the DBR to decrease its refractive index are alsopossible. In one or more embodiments, the period of the first epitaxialDBR 136 is selected to maximum reflectivity at the greenphotoluminescence wavelength. The period of the second epitaxial DBR 138is selected to maximize reflectivity at the blue electroluminescencewavelength.

Referring to FIG. 10 , bonding to a system substrate 140 is carried outas described with respect to FIG. 8 . With reference to FIG. 11 , in oneor more embodiments, the wafer 100 may be subjected to an etching stepafter substrate 102 removal, corresponding to the same stage of theprocess where deposition of wavelength selective reflective coatings132, 132 was performed in FIG. 8 . In one or more embodiments, both ofthe epitaxial DBRs 136, 138 are etched away for the first sub-pixel 105a, only the first epitaxial DBR 136 is etched away for the thirdsub-pixel 105 c, and no etching is done for the second sub-pixel 105 b.In other words the patterning of external reflector coatings asdiscussed with reference to FIG. 8 is replaced by position-selectiveetching of reflectors built into the epitaxy. In one or moreembodiments, the embodiment represented in FIGS. 9 through 10 has theadvantage that the exposed GaN surface may be textured using masklessphotoelectrochemical or masked dry etching methods to increase lightextraction efficiency. With reference to FIG. 11 , only the secondsub-pixel 105 b is textured 148, but texturing could be extended to allthree sub-pixels 105 a, 105 b, 105 c by including a sufficiently thickGaN layer in between the first and second epitaxial DBRs 136, 138 sothat it can be textured after selective etch of the first DBR in thethird sub-pixel 105 c, and by texturing the n-type layer 118, which isexposed for the first sub-pixel 105 a.

With reference to FIG. 12 , in one or more embodiments, only oneepitaxial reflector 137 is grown. In some embodiments, the epitaxialreflector 137 may be tuned for blue electroluminescence. In one or moreembodiments, the epitaxial reflector 137 may be designed to have avertical resistance low enough that it does not cause a significantvoltage drop at typical ranges of LED operating current. In one or moreembodiments, the metal contacts are designed to have high opticaltransmittance, which may be achieved by reducing the thickness of metallayers and/or the surface area covered by them. In one or moreembodiments, the sheet conductance of n-type layers 104 a, 104 b, 104 cis sufficient that metals are not required for current spreading throughthe active layers. In one or more embodiments, wavelength selectivereflector coatings 132, 134 are applied to the second subpixel 105 b andthe third subpixel 105 c. A glass substrate 160 which has beenpre-patterned with an anode contact grid and transparent thin-filmtransistor driver circuitry is bonded to the wafer, forming asemi-transparent display 300. In one or more embodiments, a commoncathode contact 168 is made to the n-type layer 118 exposed at the edgeof the wafer, as shown in FIG. 12 .

In addition to being applicable to a semi-transparent display, theembodiment illustrated in FIG. 12 has the advantage that blue photonsare more efficiently converted into green and red ones due to thepresence of selective blue reflectors on both sides of the device.

In one or more unillustrated embodiments, a device which contains LEDsof only two different colors (for example, leaving out the secondphotoluminescence quantum well 106 and the third n-type layer 104 c ofthe epitaxial growth process illustrated in FIG. 1 and the extrapost-growth processing associated with them) is formed. Although theembodiments describes above pertain to blue, red, and green colors, thedisclosure is not limited to such colors. In one or more embodiments,any combination of colors or shades of the same color (for example,three groups of QWs with 430 nm, 450 nm, and 470 nm wavelength which areall perceived by the eye as blue). In one or more embodiments, theabsorption probability of the electroluminescence of the first group ofQWs is non-negligible in the second and third groups of QWs.

FIG. 13 illustrates a process flow diagram of a method 500 ofmanufacturing an LED device according to one or more embodiments. In oneor more embodiments, a method of manufacturing a light emitting diode(LED) device begins at operation 502 where semiconductors layers aredeposited or grown on a substrate. In one or more embodiments, thesemiconductor layers comprises one or more of a substrate 102, anucleation layer 122, a defect reduction layer 120, an n-type layer 118,a dilute indium concentration layer 116, electroluminescence quantumwells 114, electron blocking layer and p-type layer 112, a tunneljunction 110, a first n-type layer 104 a, a first group ofphotoluminescence quantum wells 116, second n-type layer 104 b, a secondgroup of photoluminescence quantum wells 106, and a third n-type layer104 c. At operation 504, the semiconductor layers are etched to form atleast a first subpixel 105 a, a second subpixel 105 b, and a thirdsubpixel 105 c. The first subpixel 105 a and second subpixel 105 b areseparated by a trench 107 a, and the second subpixel 105 b and thirdsubpixel 105 c are separated by a trench 107 b. At operation 506, adielectric layer 124 is deposited on the semiconductor surface. In oneor more embodiments, at operation 508, a portion of the dielectric layeris removed in the trench 107 a, 107 b. At operation 510, a cathodecontact is formed in the trench 107 a, 107 b. At operation 512, acontact hole 128 is formed.

At operation 514, an anode contact metal 130 is deposited in the contacthole 128.

In some embodiments, the method 500 at operation 516 further comprisesattaching the wafer to a backplane and, at operation 518, formation ofan external wavelength-selective reflector coating applied to the sideof the device 100 opposite the anode contact 130.

FIGS. 14 through 21 illustrate cross-sectional views of a device 1000according to one or more embodiments. An aspect of the disclosurepertains to a method of manufacturing a LED array. Referring to FIG. 14, a LED device 1000 is manufactured containing two or more groups ofquantum wells of different emission wavelengths in the same wafer. Inone or more embodiments, a first group of quantum wells (with shortestemission wavelength) is located between a p-type layer and a firstn-type layer which forms a p-n junction with the p-type layer. In one ormore embodiments, a tunnel junction connects the p-layer of the p-njunction with a second n-type layer at a different position in theepitaxy stack versus the first n-type layer. In one or more embodiments,second and third groups of quantum wells with longer emissionwavelengths are located within the second n-type layer placed betweenthem and the p-n junction. In one or more embodiments, a tunnel junctionconnects the p-layer of the p-n junction with the second n-type layer.

In one or more embodiments, the first part of the epitaxy involves thegrowth of a nucleation layer 1022, a defect reduction layer 1020, and ann-type layer 1004 a and may be the same as in a conventional LED growthrun using a sapphire or other applicable growth substrate 1002.

The substrate 1002 may be any substrate known to one of skill in the artwhich is configured for use in the formation of LED devices. In one ormore embodiments, the substrate 1002 comprises one or more of sapphire,silicon carbide, silica (Si), quartz, magnesium oxide (MgO), zinc oxide(ZnO), spinel, and the like. In one or more embodiments, the substrate1002 is a transparent substrate. In specific embodiments, the substrate102 comprises sapphire. In one or more embodiments, the substrate 1002is not patterned prior to formation of the LEDs. Thus, in someembodiments, the substrate is 1002 not patterned and can be consideredto be flat or substantially flat. In other embodiments, the substrate1002 is a patterned substrate.

In one or more embodiments, the n-type layer 1004 a may comprise anyGroup III-V semiconductors, including binary, ternary, and quaternaryalloys of gallium (Ga), aluminum (Al), indium (In), and nitrogen (N),also referred to as III-nitride materials. Thus, in some embodiments,the n-type layer 1004 a comprises one or more of gallium nitride (GaN),aluminum nitride (AlN), indium nitride (InN), gallium aluminum nitride(GaAlN), gallium indium nitride (GaInN), aluminum gallium nitride(AlGaN), aluminum indium nitride (AlInN), indium gallium nitride(InGaN), indium aluminum nitride (InAlN), and the like. In a specificembodiment, the n-type layer 1004 a comprises gallium nitride (GaN). Inone or more embodiments, the n-type layer 1004 a is doped with n-typedopants, such as silicon (Si) or germanium (Ge). The n-type layer 1004 amay have a dopant concentration significant enough to carry an electriccurrent laterally through the layer.

In one or more embodiments, the layers of III-nitride material whichform the first LED, the second LED and the third LED are deposited byone or more of sputter deposition, atomic layer deposition (ALD),metalorganic chemical vapor deposition (MOCVD), physical vapordeposition (PVD), plasma enhanced atomic layer deposition (PEALD), andplasma enhanced chemical vapor deposition (PECVD).

In one or more embodiments, a LED device 1000 is manufactured by placingthe substrate 1002 in a metalorganic vapor-phase epitaxy (MOVPE) reactorso that the LED device layers are grown epitaxially.

In one or more embodiments, a nucleation layer 1022 is formed on thesubstrate 1002 prior to the defect reduction layer 1020. In one or moreembodiments, the nucleation layer comprises a III-nitride material. Inspecific embodiments, the nucleation layer 1022 comprises galliumnitride (GaN) or aluminum nitride (AlN).

In one or more embodiments, a first group of photoluminescence quantumwells 1006 is grown on a top surface of the n-type layer 1004 a. In oneor more embodiments, the photoluminescence quantum wells 1006 emit lighthaving a wavelength in a range of from about 600 nm to about 750 nm. Inone or more embodiments, the design of the photoluminescence quantumwells 1006 may differ from the active region of a conventional (red) LEDin that the n-type doping concentration and the number of wells may bedifferent, among other possible differences.

In one or more embodiments, a second n-type layer 1004 b may be grownover the photoluminescence quantum wells 1006. The second n-type layer1004 b has the same doping requirements as first n-type layer 1004 a,but the first n-type layer 1004 a and the second n-type layer 1004 b mayhave different thicknesses.

After formation of the n-type layer 1004 b, a group of photoluminescencequantum wells 1008 is grown. In one or more embodiments, thephotoluminescence quantum wells 1008 emit light having a wavelength in arange of from about 460 nm to about 570 nm. In one or more embodiments,the design of the photoluminescence quantum wells 1008 may differ fromthe active region of a conventional green LED in that the n-type dopingconcentration and the number of wells may be different, among otherpossible differences. In one or more embodiments, the dopingconcentration in the photoluminescence quantum wells 1008 is set highenough to avoid a significant voltage drop when this layer is part ofthe LED circuit. Subsequently, a third n-type layer 1004 c is grown onthe photoluminescence quantum wells 1008. The third n-type layer 1004 chas the same doping requirements as first n-type layer 1004 a and thesecond n-type layer 10004 b, but the first n-type layer 1004 a, thesecond n-type layer 1004 b, and the third n-type layer 1004 c may havedifferent thicknesses.

It should be noted that the positions of photoluminescence quantum wells1008 and the photoluminescence quantum wells 1006 within the epitaxystack 1001 could be interchanged in one or more embodiments. Dependingon the internal quantum efficiency (IQE) values and absorptioncoefficients of the photoluminescence quantum wells 1006 andphotoluminescence quantum wells 1008, an arrangement with the positionsof QWs interchanged versus that depicted in FIG. 14 may be favorable forsome applications.

In one or more embodiments, a plurality of electroluminescence emittingquantum wells 1014 is grown on the third n-type layer 1004 c. In one ormore embodiments, the electroluminescence emitting quantum wells 1014may be doped with n-type doping.

The electroluminescence emitting quantum wells 1014 may be formed usingany deposition technique known to one of skill in the art. Theelectroluminescence emitting quantum wells 1014 may comprise a sequenceof multiple quantum wells emitting the same wavelength of light. In oneor more embodiments, the electroluminescence emitting quantum wells 1014emit light having a wavelength in a range of from about 410 nm to about495 nm. The electroluminescence emitting quantum wells 1014 may comprisedifferent layers of indium gallium nitride (InGaN) and gallium nitride(GaN). The emission color may be controlled by the relative molefractions of indium (In) and gallium (Ga) in the InGaN layer and/or bythe thicknesses of the multiple quantum wells.

In one or more embodiments, an individual quantum well within theelectroluminescence emitting quantum wells 1014 may have an InGaNthickness in a range of from about 0.5 nm to about 10 nm and a GaNbarrier thickness in a range of from about 2 nm to about 100 nm. Thetotal number of quantum wells in the electroluminescence emittingquantum wells 1014 may be in a range of from 1 to 25.

In one or more embodiments, after the growth of the electroluminescenceemitting quantum wells 1014, electron blocking layers and p-type layers1012 are grown using deposition techniques known to one of skill in theart. In one or more embodiments, the p-type layers 1012 comprise galliumnitride (GaN).

After completing the p-type layer 1012 of the LED, the growth conditionsare then changed to grow a tunnel junction 1010. In one or moreembodiments, the tunnel junction 1010 may be similar to, but is notlimited to, tunnel junctions known to one of skill in the art. After thegrowth of the tunnel junction 1010, an n-type layer 1018 is grown on thetunnel junction 1010. The n-type layer 1018 may be thin, or it could bemuch thicker with thickness in the tens or hundreds of nanometers. Inone or more embodiments, the n-type layer 1018 is a current spreadinglayer.

In one or more embodiments, the n-type layer 1018 may comprise any GroupIII-V semiconductors, including binary, ternary, and quaternary alloysof gallium (Ga), aluminum (Al), indium (In), and nitrogen (N), alsoreferred to as III-nitride materials. Thus, in some embodiments, then-type layer 1018 comprises one or more of gallium nitride (GaN),aluminum nitride (AlN), indium nitride (InN), gallium aluminum nitride(GaAlN), gallium indium nitride (GaInN), aluminum gallium nitride(AlGaN), aluminum indium nitride (AlInN), indium gallium nitride(InGaN), indium aluminum nitride (InAlN), and the like. In a specificembodiment, the n-type layer 1018 comprises gallium nitride (GaN). Inone or more embodiments, the n-type layer 1018 is doped with n-typedopants, such as silicon (Si) or germanium (Ge). The n-type layer 1018may have a dopant concentration significant enough to carry an electriccurrent laterally through the layer.

In one or more embodiments, the doping concentration of the n-type layer1018 may be high enough to facilitate formation of ohmic contacts withcommon metals such as Al, but the doping concentration of the n-typelayer 1018 need not be as high as that of the tunnel junction 1010. Inone or more embodiments, the n-type layer 1018 could have a gradeddoping concentration or it could be divided into several sections withdifferent doping concentrations.

Referring to FIG. 15A, the epitaxy stack 1001 is bonded to a handlewafer 900. The handle wafer 900 forms a temporary bond to the n-typelayer 1018. In one or more embodiments, the handle wafer may becomprised of any material that can be processed into wafers ofadequately low roughness and warp for bonding, which remainsmechanically rigid during the bonding process. It some embodiments, itcan be advantageous to use a handle wafer made from the same material asthe growth substrate, or one that is not too different in thermal andmechanical properties from the growth substrate. In one or moreembodiments, the bonding process typically involves coating one or morelayers on the handle wafer and the back of the growth substrate prior tobonding. Various processes are possible and may utilize metal eutectics,polymers, or oxide-oxide bonds.

With reference to FIG. 15B, the substrate 1002 is removed. In someembodiments, the substrate 1002 may be removed by any technique known tothe skilled artisan, including, but not limited to laser lift-off,selective chemical etching, and the like. In one or more embodiments,the nucleation layer 1022 and the defect reduction layer 1020 areremoved. The nucleation layer 1022 and the defect reduction layer 1020may be removed by any suitable technique known to the skill artisanincluding, but not limited to, dry etching.

Referring to FIG. 16 , a plurality of subpixels is formed by etching afirst subpixel 1005 a, a second subpixel 1005 b, and a third subpixel1005 c into the wafer 1001. In one or more embodiments, the firstsubpixel 1005 a and the second subpixel 1005 b are separated by a trench1007 a. In some embodiments, the trench 1007 a may be formed using aconventional directional etching process, such as dry etching. Thetrench 1007 a may be any suitable depth and may extend from the topsurface of the first n-type layer 1004 a through the n-type layer 1018to the handle wafer 900. The trench 1007 a may comprise at least onesidewall 1009 a and a bottom surface 1011 a. In one or more embodiments,the second subpixel 1005 b and the third subpixel 1005 c are separatedby a trench 1007 b. In some embodiments, the trench 1007 b may be formedusing a conventional directional etching process, such as dry etching.The trench 1007 b may be any suitable depth and may extend from the topsurface of the first n-type layer 1004 a through the n-type layer 1018to the handle wafer 900. The trench 1007 b may comprise at least onesidewall 1009 b and a bottom surface 1011 b.

In one or more embodiments, the first subpixel 1005 a may have a height(thickness) that is less than the height (thickness) of the secondsubpixel 1005 b and less than the height (thickness) of the thirdsubpixel 1005 c. In one or more embodiments, the third subpixel 1005 cmay have a height (thickness) that is less than the height (thickness)of the second subpixel 1005 b.

In one or more embodiments, the etched surface (trench 1007 a, 1007 b)may have an angle of inclination up to 45 degrees. In some embodiments,the etched surface (trench 1007 a, 1007 b) may be substantiallycompletely vertical.

In one or more embodiments, the formation of the plurality of subpixels1005 a, 1005 b, 1005 c involves an additional etching step compared toconventional LED manufacturing methods. In one or more embodiments, theadditional etching step removes the first group of photoluminescentquantum wells 1008 and the second group of photoluminescent quantumwells 1006 at a first set of positions 1005 a on the handle wafer 900,removes the second group of photoluminescent quantum wells 1006 at asecond set of positions 1005 c on the handle wafer 900, and leavesunetched a third set of positions 1005 b on the handle wafer. Thethickness of material that needs to be etched from the first set ofpositions 1005 a is thicker than that to be removed from the second setof positions 1005 c. The thickness difference may be accommodated eitherby separating the additional etch process into two separate etch steps,or by coating a sacrificial layer onto the second set of positions 1005c to reduce the depth of material etched at those positions in a singleetch step. Dry etching using process conditions which favor a highvertical/lateral etch rate may be used for the additional etching step.This additional etching step may be one of the first steps in theprocess, or it may come later in the process (for example, after themesa etch to expose the n-layer under the p-n junction).

In one or more embodiments, the first subpixel 1005 a is a mesacomprising electroluminescence emitting quantum wells 1014. Morespecifically, the first subpixel 1005 a comprises a first mesa includinga third n-type layer 1004 c on electroluminescence emitting quantumwells 1014 on a tunnel junction 1010 on electron blocking layers andp-type layers 1012. The p-type layers 112 may be on an n-type layer 118on the handle wafer 900.

In one or more embodiments, the second subpixel 1005 b is a mesacomprising a first group of photoluminescent quantum wells 1008 and asecond group of photoluminescent quantum wells 1006 on anelectroluminescent quantum well 1014. More specifically, the secondsubpixel 1005 b comprises a second mesa including a first n-type layer1004 a on the second group of photoluminescent quantum wells 1006, asecond n-type layer 1004 b on the first group of photoluminescentquantum wells 1008, a third n-type layer 1004 b on a group ofelectroluminescence emitting quantum wells 1014. The group ofelectroluminescence emitting quantum wells 1014 may be on electronblocking layers and p-type layers 112 on a tunnel junction 1010 on ann-type layer 118 on the handle wafer 900.

In one or more embodiments, the third subpixel 1005 c is a mesacomprising a first group of photoluminescent quantum wells 1008 on anelectroluminescent quantum well 1014. More specifically, the thirdsubpixel 1005 c comprises a third mesa including a second n-type layer1004 b on the first group of photoluminescent quantum wells 1008, athird n-type layer 1004 c on a group of electroluminescence emittingquantum wells 1014. The group of electroluminescence emitting quantumwells 1014 may be on electron blocking layers and p-type layers 112 on atunnel junction 1010 on an n-type layer 118 on the handle wafer 900.

In one or more embodiments, a p-type layer activation annealing step maybe performed after the plurality of subpixels are etched because it isdifficult for hydrogen to pass through n-type layers 1004 a, 1004 b,1005 c and annealing after the mesa etch allows hydrogen to escapelaterally from the etched sidewalls.

FIG. 17 shows formation of a dielectric layer 1024 on the pluralities ofsubpixels 1005 a, 1005 b, 1005 c and in the trench 1007 a, 1007 b. Thedielectric layer 1024 may be formed using a conventional depositiontechnique, such as, for example, CVD, PECVD, ALD, evaporation,sputtering, chemical solution deposition, spin-on deposition, or otherlike processes.

In one or more embodiments, the dielectric layer 1024 may comprise anysuitable dielectric material known to the skilled artisan. In someembodiments, the dielectric material comprises one of more of siliconnitride (SiN), titanium oxide (TiO_(x)), niobium oxide (NbO_(x)),aluminum oxide (AlO_(x)), hafnium oxide (HfO_(x)), tantalum oxide(TaO_(x)), aluminum nitride (AlN), silicon oxide (SiO_(x)), andhafnium-doped silicon dioxide (HfSiO_(x)). In one or more embodiments,the dielectric layer 1024 has a thickness greater than about 100 nm, orgreater than about 500 nm, or greater than about 1000 nm.

In one or more embodiments, the dielectric layer 1024 is substantiallyconformal. As used herein, a layer which is “substantially conformal”refers to a layer where the thickness is about the same throughout(e.g., on the top surface of each subpixel, on the at least one sidewall1009 a, 1009 b, and on the bottom surface 1011 a, 1011 b of the trench1007 a, 1007 b). A layer which is substantially conformal varies inthickness by less than or equal to about 5%, 2%, 1% or 0.5%.

In some embodiments, the dielectric layer 1024 forms on the bottomsurface 1011 a, 1011 b of the trench 1007 a, 1007 b. In otherembodiments, the dielectric layer 1024 is not on the bottom surface 1011a, 1011 b of the trench 1007 a, 1007 b and the handle wafer 900 isexposed on the bottom surface of the trench 1007 a, 1007 b. Referring toFIG. 18 , portions of the dielectric layer 1024 may be removed from thebottom surface 1011 a, 1011 b and at least one sidewall 1009 a, 1009 bof the trench 1007 a, 1007 b. The portions of the dielectric layer 1024may be removed using a conventional directional etching process, such asdry etching. In one or more embodiments, when portions of the dielectriclayer 1024 are removed from the bottom surface 1011 a, 1011 b and atleast one sidewall 1009 a, 1009 b of the trench 1007 a, 1007 b, anexposed portion 1025 a, 1025 b is formed. The exposed portion 1025 a,1025 b may include portions of the n-type layer 1018 and the handlewafer 900 may be exposed in the trench 1007 a, 1007 b.

Referring to FIG. 19 , in one or more embodiments, an anode contactmetal 1026 is deposited on the exposed portion 1025 in the trench 1007a, 1007 b. In one or more embodiments, the anode contact metal 1026 maycomprise any suitable material known to the skilled artisan. In one ormore embodiments, the anode contact metal 1026 comprises a metalselected from one or more of silver (Ag), aluminum (Al), gold (Au),platinum (Pt), and palladium (Pd). In specific embodiments, the anodecontact metal 1026 comprises silver (Ag) or aluminum (Al). In someembodiments, additional metals may be added in small quantities to theanode contact metal as adhesion promoters. Such adhesion promoters,include, but are not limited to, one or more of nickel (Ni), titanium(Ti), and chromium (Cr).

FIG. 20 shows formation of a contact hole 1028 in the dielectric layer1024, exposing a top surface of the n-type layer 1004. In someembodiments a first contact hole 1028 a is formed in the dielectriclayer 1024 of the first subpixel 1005 a, exposing a top surface of thethird n-type layer 104 c. A second contact hole 1028 b may be formed inthe dielectric layer 1024 of the second subpixel 1005 b, exposing a topsurface of the first n-type layer 1004 a. A third contact hole 1028 cmay be formed in the dielectric layer 1024 of the third subpixel 1005 c,exposing a top surface of the second n-type layer 1004 b. The contacthole 1028 a, 1028 b, 1028 c may be formed using a conventionaldirectional etching process, such as dry etching.

Referring to FIG. 21 , a cathode contact metal 1030 is deposited in thecontact hole 1028. In one or more embodiments, the cathode contact metal1030 may comprise any suitable material known to the skilled artisan. Inone or more embodiments, the cathode contact metal 1030 comprises ann-contact material selected from one or more of aluminum (Al), titanium(Ti) and chromium (Cr).

In one or more embodiments, the cathode contact 1030 and the anodecontact 1026 may be made with the same metal in the same deposition andlift-off steps.

The dielectric passivation layer 1024 is shown as a single layer in theFigures, but it could alternatively be implemented as a multilayercoating of high and low refractive index materials with thicknessesoptimized for maximum reflectivity in blue wavelengths. If implementedas a single layer, the optical thickness of the dielectric passivationlayer 1024 may be co-optimized with the cathode metal 1030 to maximizereflectivity at blue wavelengths. The cathode contact 1030 may be madeto the n-type layer on the sides of the mesas 1005 a, 1005 b, 1005 c,making possible the use of a single mesa etch step to isolate the LEDsfrom each other and expose the cathode contact for metallization.

Referring to FIG. 22 , in later stages of processing, the spaces betweenthe mesas 1005 a, 1005 b, 1005 c are filled with an electricallyconductive material 1046, which could be, for example, electroplatedcopper (Cu). The entire wafer 1000 or a piece of the wafer 1000, whichcould be as small as an individual pixel containing three microLEDsub-pixels, are bonded to a system substrate 1040 such as a displaybackplane to form a system 2000. An array of landing pads 1042, 1044 isarranged on the system substrate 1040 with dimensions aligned to thoseof the bonding pads on the LED wafer 1000. The landing pads 1042, 1044may be connecting to display driver circuitry in the system substrate1040. The landing pads 1042, 1044 may include sub-pixels of differentheights to accommodate the differences in heights of the LEDs on thewafer, as shown in FIG. 22 . Alternatively, the landing pads 1042, 1044may be made from a material that is soft enough to accommodate theheight differences by mechanical deformation in the bonding process. Inone or more embodiments, the bonding mechanism may be based onapplication of pressure, localized heating, or a combination of the two.

Referring to FIG. 22 , in one or more embodiments, after bonding, thehandle wafer 900 is removed using any suitable technique known to theskilled artisan, such as by selective chemical etching. In one or moreembodiments, wavelength selective reflector coatings 1032, 1034 areapplied to the exposed surfaces of the sub-pixels 1005 b, 1005 c toprevent color contamination of those pixels with shorter wavelengthlight that is not completely absorbed in the QWs of longer wavelength.In some embodiments, the wavelength selective reflector coatings 1032,1034 may comprise dichroic mirrors.

In one or more specific embodiments, the wavelength selective reflectorcoating 1032 for the third sub-pixel 1005 c may be a distributed Braggreflector (DBR) consisting of a repeated stack of dielectric materialswith high and low refractive indices and thicknesses optimized tomaximize reflectivity at the blue electroluminescence peak wavelength.In one or more embodiments, the second sub-pixel 1005 b may use twoconnected distributed Bragg reflectors (DBR) optimized for highreflectivity at blue and green wavelengths, respectively, as wavelengthselective reflector coatings 1032, 1034. In one or more embodiments, thewavelength selective reflector coatings 1032, 1034 may be patterned bylithographic methods.

FIG. 23 illustrates an alternative embodiment. The epitaxial growthillustrated in FIG. 23 differs slightly from that of FIGS. 14 through 22. Referring to FIG. 23 , in one or more embodiments, two epitaxialreflectors 1036, 1038 are grown. In some embodiments, at least onen-type layer 1004 is formed on the epitaxial reflectors 1036, 1038. Inone or more embodiments, the epitaxial reflectors 1036, 1038 aredichroic mirrors. In specific embodiments, the epitaxial reflectors1036, 1038 may be distributed Bragg reflectors (DBR) comprised of asequence of alternating layers III-nitride materials with differentrefractive indices, such as, but not limited to, gallium nitride (GaN)and aluminum gallium nitride (AlGaN) or aluminum indium nitride (AlInN),or mixtures thereof. In one or more embodiments, implementations inwhich post-growth processing to oxidize or introduce porosity into oneof the materials of the DBR to decrease its refractive index are alsopossible. In one or more embodiments, the period of the first epitaxialDBR 1036 is selected to maximum reflectivity at the greenphotoluminescence wavelength. The period of the second epitaxial DBR1038 is selected to maximize reflectivity at the blueelectroluminescence wavelength. In one or more embodiments, theepitaxial reflectors 1036, 1038 are advantageous in implementations thatfeature surface texturing, as depicted in FIG. 25 . In embodiments thatdue not feature surface texturing, separated deposited mirrors that arenot epitaxial are used.

Referring to FIG. 24 , bonding to a system substrate 1040 is carried outas described with respect to FIG. 22 . With reference to FIG. 25 , inone or more embodiments, the wafer 1000 may be subjected to an etchingstep after removal of the handle wafer 900, corresponding to the samestage of the process where deposition of wavelength selective reflectivecoatings 1032, 1032 was performed in FIG. 22 . In one or moreembodiments, both of the epitaxial DBRs 1036, 1038 are etched away forthe first sub-pixel 1005 a, only the first epitaxial DBR 1036 is etchedaway for the third sub-pixel 1005 c, and no etching is done for thesecond sub-pixel 1005 b. In other words the patterning of externalreflector coatings as discussed with reference to FIG. 25 is replaced byposition-selective etching of reflectors built into the epitaxy. In oneor more embodiments, the embodiment represented in FIGS. 23 through 25has the advantage that the exposed GaN surface 1004 may be texturedusing maskless photoelectrochemical or masked dry etching methods toincrease light extraction efficiency. With reference to FIG. 25 , onlythe second sub-pixel 1005 b is textured 1048, but texturing could beextended to all three sub-pixels 1005 a, 1005 b, 1005 c by including asufficiently thick GaN layer in between the first and second epitaxialDBRs 1036, 1038 so that it can be textured after selective etch of thefirst DBR in the third sub-pixel 1005 c, and by texturing the n-typelayer 1018, which is exposed for the first sub-pixel 1005 a.

With reference to FIG. 26 , in one or more embodiments, only oneepitaxial reflector 1037 is grown. In some embodiments, the epitaxialreflector 1037 may be tuned for blue electroluminescence. In one or moreembodiments, the epitaxial reflector 1037 may be designed to have avertical resistance low enough that it does not cause a significantvoltage drop at typical ranges of LED operating current. In one or moreembodiments, the metal contacts are designed to have high opticaltransmittance, which may be achieved by reducing the thickness of metallayers and/or the surface area covered by them. In one or moreembodiments, the sheet conductance of n-type layers 1004 a, 1004 b, 1004c is sufficient that metals are not required for current spreadingthrough the active layers. In one or more embodiments, wavelengthselective reflector coatings 1032, 1034 are applied to the secondsubpixel 1005 b and the third subpixel 1005 c. A glass substrate 1060which has been pre-patterned with an anode contact grid and transparentthin-film transistor driver circuitry is bonded to the wafer, forming asemi-transparent display 3000. In one or more embodiments, a commoncathode contact 1068 is made to the n-type layer 1018 exposed at theedge of the wafer, as shown in FIG. 26 .

In addition to being applicable to a semi-transparent display, theembodiment illustrated in FIG. 26 has the advantage that blue photonsare more efficiently converted into green and red ones due to thepresence of selective blue reflectors on both sides of the device.

In one or more unillustrated embodiments, a device which contains LEDsof only two different colors (for example, leaving out the secondphotoluminescence quantum well 1006 and the third n-type layer 1004 c ofthe epitaxial growth process illustrated in FIG. 14 and the extrapost-growth processing associated with them) is formed. Although theembodiments describes above pertain to blue, red, and green colors, thedisclosure is not limited to such colors. In one or more embodiments,any combination of colors or shades of the same color (for example,three groups of QWs with 430 nm, 450 nm, and 470 nm wavelength which areall perceived by the eye as blue). In one or more embodiments, theabsorption probability of the electroluminescence of the first group ofQWs is non-negligible in the second and third groups of QWs.

FIG. 27 illustrates a process flow diagram of a method 5000 ofmanufacturing an LED device according to one or more embodiments. In oneor more embodiments, a method of manufacturing a light emitting diode(LED) device begins at operation 5002 where semiconductors layers aredeposited or grown on a substrate. In one or more embodiments, thesemiconductor layers comprises one or more of a substrate 1002, anucleation layer 1022, a defect reduction layer 1020, an n-type layer1018, a dilute indium concentration layer 1016, electroluminescencequantum wells 1014, electron blocking layer and p-type layer 1012, atunnel junction 1010, a first n-type layer 1004 a, a first group ofphotoluminescence quantum wells 1008, second n-type layer 1004 b, asecond group of photoluminescence quantum wells 1006, and a third n-typelayer 1004 c. At operation 5004, the semiconductor layers are etched toform at least a first subpixel 1005 a, a second subpixel 1005 b, and athird subpixel 1005 c. The first subpixel 1005 a and second subpixel1005 b are separated by a trench 1007 a, and the second subpixel 1005 band third subpixel 1005 c are separated by a trench 1007 b. At operation5006, a dielectric layer 1024 is deposited on the semiconductor surface.In one or more embodiments, at operation 5008, a portion of thedielectric layer is removed in the trench 1007 a, 1007 b. At operation5010, an anode contact is formed in the trench 1007 a, 1007 b. Atoperation 5012, a contact hole 1028 is formed.

At operation 5014, a cathode contact metal 1030 is deposited in thecontact hole 1028.

In some embodiments, the method 5000 at operation 5016 further comprisesattaching the wafer to a backplane and, at operation 5018, formation ofan external wavelength-selective reflector coating applied to the sideof the device 1000.

Another aspect of the disclosure pertains to an electronics system. Inone or more embodiments, an electronic system comprises the LED devicesand arrays described herein and driver circuitry configured to provideindependent voltages to one or more of p-contact layers. In one or moreembodiments, the electronic system is selected from the group consistingof a LED-based luminaire, a light emitting strip, a light emittingsheet, an optical display, and a microLED display.

The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing the materials and methods discussed herein(especially in the context of the following claims) are to be construedto cover both the singular and the plural, unless otherwise indicatedherein or clearly contradicted by context. Recitation of ranges ofvalues herein are merely intended to serve as a shorthand method ofreferring individually to each separate value falling within the range,unless otherwise indicated herein, and each separate value isincorporated into the specification as if it were individually recitedherein. All methods described herein can be performed in any suitableorder unless otherwise indicated herein or otherwise clearlycontradicted by context. The use of any and all examples, or exemplarylanguage (e.g., “such as”) provided herein, is intended merely to betterilluminate the materials and methods and does not pose a limitation onthe scope unless otherwise claimed. No language in the specificationshould be construed as indicating any non-claimed element as essentialto the practice of the disclosed materials and methods.

Reference throughout this specification to the terms first, second,third, etc. may be used herein to describe various elements, and theseelements should not be limited by these terms. These terms may be usedto distinguish one element from another.

Reference throughout this specification to a layer, region, or substrateas being “on” or extending “onto” another element, means that it may bedirectly on or extend directly onto the other element or interveningelements may also be present. When an element is referred to as being“directly on” or extending “directly onto” another element, there may beno intervening elements present. Furthermore, when an element isreferred to as being “connected” or “coupled” to another element, it maybe directly connected or coupled to the other element and/or connectedor coupled to the other element via one or more intervening elements.When an element is referred to as being “directly connected” or“directly coupled” to another element, there are no intervening elementspresent between the element and the other element. It will be understoodthat these terms are intended to encompass different orientations of theelement in addition to any orientation depicted in the figures.

Relative terms such as “below,” “above,” “upper,”, “lower,” “horizontal”or “vertical” may be used herein to describe a relationship of oneelement, layer, or region to another element, layer, or region asillustrated in the figures. It will be understood that these terms areintended to encompass different orientations of the device in additionto the orientation depicted in the figures.

Reference throughout this specification to “one embodiment,” “certainembodiments,” “one or more embodiments” or “an embodiment” means that aparticular feature, structure, material, or characteristic described inconnection with the embodiment is included in at least one embodiment ofthe disclosure. Thus, the appearances of the phrases such as “in one ormore embodiments,” “in certain embodiments,” “in one embodiment” or “inan embodiment” in various places throughout this specification are notnecessarily referring to the same embodiment of the disclosure. In oneor more embodiments, the particular features, structures, materials, orcharacteristics are combined in any suitable manner.

Although the disclosure herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent disclosure. It will be apparent to those skilled in the art thatvarious modifications and variations can be made to the method andapparatus of the present disclosure without departing from the spiritand scope of the disclosure. Thus, it is intended that the presentdisclosure include modifications and variations that are within thescope of the appended claims and their equivalents.

What is claimed is:
 1. A system comprising: a light emitting diode (LED)device comprising a substrate having a first sub-pixel on a first mesa,a second sub-pixel on a second mesa, and a third sub-pixel on a thirdmesa thereon, a first trench separating the first sub-pixel and thesecond sub-pixel, a second trench separating the second sub-pixel andthe third sub-pixel, and a dielectric layer formed over at least aportion of the first sub-pixel, the second sub-pixel, and the thirdsub-pixel, wherein the first mesa has a first mesa tunnel junction on afirst mesa electroluminescent quantum well, the second mesa has a secondmesa first photoluminescent quantum well and a second mesa secondphotoluminescent quantum well on a second mesa tunnel junction on asecond mesa electroluminescent quantum well, and the third mesa has athird mesa photoluminescent quantum well on a third mesa tunnel junctionon a third mesa electroluminescent quantum well; an LED device attachregion having a first electrode coupled to a first anode contact on thefirst sub-pixel, a second electrode coupled to a second anode contact onthe second sub-pixel, and a third electrode coupled to a third anodecontact on the third sub-pixel; and driver circuitry configured toprovide independent voltages to one or more of the first electrode, thesecond electrode, and the third electrode.
 2. The system of claim 1,further comprising a first dichroic mirror on the substrate and a seconddichroic mirror on the first dichroic mirror.
 3. The system of claim 1,further comprising a nucleation layer on the substrate and a defectreduction layer on the nucleation layer.
 4. The system of claim 1,wherein the first mesa electroluminescent quantum well, the second mesaelectroluminescent quantum well, and the third mesa electroluminescentquantum well independently emit light having a wavelength in a range offrom about 410 nm to about 495 nm.
 5. The system of claim 1, wherein thesecond mesa first photoluminescent quantum well and the third mesaphotoluminescent quantum well independently emit light having awavelength in a range of from about 460 nm to about 570 nm.
 6. Thesystem of claim 1, wherein the second mesa second photoluminescentquantum well emits light having a wavelength in a range of from about600 nm to about 750 nm.
 7. The system of claim 1, further comprising afirst cathode contact in the first trench and a second cathode contactin the second trench.
 8. The system of claim 1, wherein the second mesafirst photoluminescent quantum well, the second mesa secondphotoluminescent quantum well, and the third mesa photoluminescentquantum well independently comprise multiple quantum wells emitting asame wavelength of light.
 9. The system of claim 1, wherein thesubstrate is a transparent substrate.
 10. A system comprising: a lightemitting diode (LED) device comprising a substrate having a firstsub-pixel on a first mesa, a second sub-pixel on a second mesa, and athird sub-pixel on a third mesa thereon, a first trench separating thefirst sub-pixel and the second sub-pixel, a second trench separating thesecond sub-pixel and the third sub-pixel, and a dielectric layer formedover at least a portion of the first sub-pixel, the second sub-pixel,and the third sub-pixel, wherein the first mesa has a first mesaelectroluminescent quantum well on a first mesa tunnel junction, thesecond mesa has a second mesa first photoluminescent quantum well and asecond mesa second photoluminescent quantum well on a second mesaelectroluminescent quantum well on a second mesa tunnel junction, andthe third mesa has a third mesa photoluminescent quantum well on a thirdmesa electroluminescent quantum well on a third mesa tunnel junction; anLED device attach region having a first electrode coupled to a firstcathode contact on the first sub-pixel, a second electrode coupled to asecond cathode contact on the second sub-pixel, and a third electrodecoupled to a third cathode contact on the third sub-pixel; and drivercircuitry configured to provide independent voltages to one or more ofthe first electrode, the second electrode, and the third electrode. 11.The system of claim 10, wherein the first mesa electroluminescentquantum well, the second mesa electroluminescent quantum well, and thethird mesa electroluminescent quantum well independently emit lighthaving a wavelength in a range of from about 410 nm to about 495 nm. 12.The system of claim 10, wherein the second mesa first photoluminescentquantum well and the third mesa photoluminescent quantum wellindependently emit light having a wavelength in a range of from about460 nm to about 570 nm.
 13. The system of claim 10, wherein the secondmesa second photoluminescent quantum well emits light having awavelength in a range of from about 600 nm to about 750 nm.
 14. Thesystem of claim 10, further comprising a first anode contact in thefirst trench and a second anode contact in the second trench.
 15. Thesystem of claim 10, wherein the second mesa first photoluminescentquantum well, the second mesa second photoluminescent quantum well, andthe third mesa photoluminescent quantum well independently comprisemultiple quantum wells emitting a same wavelength of light.
 16. Thesystem of claim 10, wherein the substrate is a transparent substrate.